1. Field of the Invention
The invention relates generally to medical apparatus and especially to a diagnostic and monitoring device for electronically measuring body temperature and pulse frequency.
The patient monitoring system of this invention utilizes a temperature responsive component, such as an electrothermic transducer for detecting internal body temperature and an electroacoustic transducer for sensing pulse rate or frequency.
2. Description of the Prior Art
Currently used electronic patient monitoring systems are commonly employed in intensive care quarters and coronary care units. The equipment used frequently includes one or more pieces of bedside apparatus hard-wired to a central monitoring position which is manned by a nurse or otherwise provided with an alarm signal. Similar types of equipment are also applied in operating room systems. The aforementioned medical apparatus is generally adapted for the simultaneous monitoring of several different body functions, and the patient must be fitted with numerous probes, electrodes, hypodermic needles and other sensing devices, the attachment of which to the patient can be cumbersome, time consuming and may require the services of a nurse or trained technician. Furthermore, the circumstances under which this equipment is used are usually in critical situations and concern about patient disturbance or discomfort would not be a prime consideration. Additionally, this medical equipment is rather expensive and consequently is not available for hospital patients outside of the special care units as above noted.
Another system for monitoring the temperature of a patient employs a radio frequency communication link between a transmitter carried by the patient and is discussed in U.S. Pat. No. 3,921,621. A problem with this last mentioned system is that it would be subject to radio interference which is generated by hospital equipment.
The apparatus of this invention is designed for the detention and measuring of pulse rate and internal body temperature under ordinary circumstances within or outside of the hospital.
The pule rate is conventionally counted at locations where an artery approaches the surface of the body. Such locations in the upper extremity or limb anatomically occur at the radial artery in the wrist and at the brachial artery along the inner or medial side of the arm near the biceps. The instant invention in contrast detects blood pressure change in the arterial circulation system at a main trunk located in close proximity to the heart. Accordingly, the alternate expansion and contraction of the artery which constitutes the pulse is measured as this pressure change is brought about by ejection of blood from the heart into the aorta and propagates as a wave through the blood column. The blood flows through a conduit or tubular channel constituting the aorta and into a subclavian artery through the axillary artery and into the brachial artery during its flow down the arm and toward the hand. By positioning a pulse sensing unit within the axillary space or fossa formed between the medial or inner side of the arm and the lateral surface of the chest wall commonly referred to as the underarm region, an electroacoustic transducer can sense the blood flow through the axillary artery. Since a fascia or band of connective tissue invests or envelops the axillary artery in a sheath which includes other large vessels and nerves, it has been found that by positioning the transducer at the apex of this pyramidal compartment or axillary space the closest proximity to the axillary artery can be reached. Furthermore, the adipose or fatty padding tissue in the fossa will surround the temperature responsive element and thus provide a reliable indication of the internal body temperature. It should thus be apparent that by positioning both the pulse detecting and temperature responsive components at the apex of the axillary space both of these physiological variables can be determined. A feature of this invention is the recognition and utilization of the fossa or depression forming the armpit as a desirable anatomic location for positioning of such instrument.
A further feature of this invention is that the transducer is mounted in a disposable flexible cloth shoulder strap which can be positioned on the patient upon entering the hospital and remain with the patient during his stay. A nurse or attendant carrying a hand-held display console can quickly and effectively determine the temperature and pulse rate of each patient by interconnecting a removable plug with a mating receptacle on the shoulder strap. Within about fifteen seconds a determination can be made as to these temperature and pulse rate values and the patient need not be moved or disturbed while obtaining such readings.